Electrical oil composition

ABSTRACT

An electrical oil composition comprising: A) dc-asphalted cylinder oil (DACO) having a benzo [a] pyrene content of not more than 1 mg/kg and a total content of benz [a] anthracene, chrysene, benzo [b] fluoranthene, benzo [j] fluoranthene, benzo [k] fluoranthene, benzo [c] pyrene, benzo [a] pyrene and dibenz [a, h] anthracene of not more than 10 mg/kg; and B) one or more base oils each having a viscosity of not more than 4.0 mm 2 /s at 100° C.

The present invention relates to an electrical oil composition.

Many types of electrical equipment contain an electrical oil compositionfor dissipating the heat generated by energised components, forinsulating the energised components from the equipment enclosure andfrom other internal parts and devices, and combinations thereof.Examples of electrical equipment include, but are not limited to,transformers, capacitors, switches, regulators, circuit breakers,cables, reclosers, rectifiers, reactors, x-ray equipment, andcombinations thereof.

A transformer generally transfers electric power from one circuit toanother electromagnetically. Transformers are generally used in thetransmission of electrical power.

Large transformers generally require insulation of coils, conductors,and combinations thereof, in order to protect the transformer at normaloperating voltages, during temperature overvoltages, during transientovervoltages, and combinations thereof. Transient overvoltages mayresult from lightning strikes, switching operations, and combinationsthereof. When insulation fails, an internal fault or short circuit mayoccur. Such occurrences may cause the equipment to fail, typicallyleading to system outages and possibly endangering persons in thevicinity of the equipment.

In order to effectively transfer heat away from a transformer core andcoil assembly and to maintain an acceptable operating temperature,conventional transformers use relatively large volumes of an electricaloil composition as insulation.

A demand is acknowledged for high oxidation resistant oil products foruse as electrical oil compositions, in particular as a transformer oilor a switch gear oil, preferably without high additive treat rates dueto adverse effects on other properties than oxidation stability.

Good oxidation stability may expressed by low acid formation and/or lowsludge formation and low temperature viscosity values.

WO-A-01/54138 describes an electrical oil composition which is said tohave improved oxidation and electrical resistance. Said electrical oilcomposition comprises a blend of (A) a substantially nitrogen andsulphur free, paraffinic or naphthenic base oil boiling in theelectrical oil boiling range, and (B) a hydrofined light gas oil (LGO)boiling in the range of about 200° C. to about 400° C. and having asulphur to basic nitrogen ratio (S/BN) greater than 100:1, thehydrofined LGO being present in an amount sufficient to provide a blendhaving greater than about 0.03 wt % sulphur.

However, many electrical oil compositions have been made from blends ofnaphthenic or paraffinic base oils with distillate aromatic extracts(DAE).

Distillate aromatic extracts have very high aromatic contents, typicallyat least 70 wt. %.

By the term “aromatic” it is meant a molecule composed primarily ofcarbon and hydrogen which comprises at least one ring which composed ofconjugated unsaturated carbon bonds, such as compounds containing abenzene moiety, polynuclear aromatics or polyaromatic compounds, i.e.compounds comprising more than one aromatic ring fused together, such asanthracene based moieties, are also included in this definition ofaromatic. Such molecules may comprise sulphur as a heteroatom.

Distillate aromatic extracts are obtained as a by-product of the processof solvent extraction of vacuum distillates used as a raw material forthe manufacture of lubricant base oils. Such distillate aromaticextracts generally contain high concentrations of polynuclear aromatics,typically from 10 to 25 wt. %, as measured by IP 346 method.

Certain polynuclear aromatics (PNA), which are also known as higheraromatic rings, polycyclic aromatics (PCA) or polyaromatic hydrocarbons(PAH), are known carcinogens.

Distillate aromatic extracts are classified as “carcinogenic” accordingto the European legislation (EU Substance Directive 67/548/EEC) and mustbe labelled with the risk phrase “R45” (may cause cancer) and the label“T” (toxic, skull and crossbones) in Europe.

Accordingly, electrical oil compositions comprising 0.1 wt. % or more ofdistillate aromatic extracts must also be labelled with the risk phrase“R45” (may cause cancer) and the label “T” (toxic, skull and crossbones)in Europe due to the levels of polynuclear aromatics, and in particularpolyaromatic hydrocarbons therein.

From the viewpoint of health, safety and environmental impact, it ishighly desirable to use alternatives to distillate aromatic extracts asblending components in electrical oil compositions, which electrical oilcompositions not only have low polynuclear aromatic content, andtherefore also low carcinogenicity, but which also still have goodoxidation stability, preferably without high additive treat rates due toadverse effects these can have on other properties than oxidationstability.

The present Application provides an electrical oil compositioncomprising (A) de-asphalted cylinder oil (DACO) having a benzo[a]pyrenecontent of not more than 1 mg/kg and a total content ofbenz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene,benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene and dibenz[a,h]anthracene of not more than 10 mg/kg; and (B) one or more base oilseach having a viscosity of not more than 4.0 mm²/s at 100° C.

In this respect it is noted that GB 716 979 (published in 1954), U.S.Pat. No. 2,725,345 (published in 1955) and GB 1 237 291 (published in1971) disclose lubricating oil compositions comprising de-asphalted oils(optionally subjected to solvent extraction treatment) and a base oil.However, the lubricating oil composition as described in the abovepublications would need to be classified as “carcinogenic” and “toxic”as outlined above in view of the preparation methods as used at the timewhich resulted in relatively high polynuclear aromatics contents. Thishas also been the reason that in the last decades de-asphalted(cylinder) oils have not been used in lubricating oil compositions andthe like.

Furthermore, the above 3 publications do not teach or suggest the lowbenzo[a]pyrene contents as required according to the present invention.

The de-asphalted cylinder oil (DACO) according to the present inventionmay be prepared by de-asphalting a mineral-derived vacuum residue toobtain a de-asphalted oil (DAO), solvent-extracting the de-asphalted oiland obtaining the de-asphalted cylinder oil (DACO) extract.

The de-asphalted oil (DAO) used is defined as the product of ade-asphalting process step wherein asphalt is removed from a reducedcrude petroleum feed or from the residue, bottom fraction, of a vacuumdistillation of a crude petroleum feed (hereinafter referred to as“mineral-derived vacuum residues”).

The de-asphalting process utilises a light hydrocarbon liquid solvent,for example propane, for asphalt compounds.

De-asphalting processes are well known and for example, are described in“Lubricant base oil and wax processing”, Avilino Sequeira, Jr., MarcelDekker, Inc, New York, 1994, ISBN 0-8247-9256-4, pages 53-80.

The de-asphalted oil undergoes solvent extraction, wherein residualaromatic extract known as de-asphalted cylinder oil (DACO) is removedtherefrom.

Examples of solvent extraction process that may be conveniently usedinclude furfural or NMP solvent extraction processes or other solventextraction processes, for example, as described in Chapter 5 of“Lubricant base oil and wax processing”, Avilino Sequeira, Jr., MarcelDekker, Inc, New York, 1994, ISBN 0-8247-9256-4.

The benzo[a]pyrene content and 8 PAH content may be measured in thede-asphalted cylinder oil by GC/MS analysis. For example, this techniqueis commercially available at Biochemisches Institut furUmweltcarcinogene (Prof. Dr. Gernot Grimmer-Stiftung), Lurup 4, D-22927Grosshansdorf, Germany.

The amount of polyaromatic hydrocarbons subsequently present in thede-asphalted cylinder oil may be controlled during isolation of themineral-derived vacuum residue by appropriate selection of the cut widthof the highest boiling distillate fraction.

The de-asphalted cylinder oil preferably has a sulphur content in therange of from 0.5 to 5 wt. %, more preferably in the range of from 3 to4.5 wt. %, as measured by ISO 14596, based on the total weight of thede-asphalted cylinder oil.

The kinematic viscosity at 100° C. of the de-asphalted cylinder oil ispreferably less than 100 mm²/s, more preferably in the range of from 35to 90 mm²/s.

Kinematic viscosity at 100° C. as mentioned herein may be convenientlymeasured in accordance with ISO 3104.

The flash point of the de-asphalted cylinder oil is preferably above250° C., more preferably above 280° C. and most preferably above 290°C., as measured by the Cleveland Open Cap (COC) method, ISO 2592.

The de-asphalted cylinder oil (A) is preferably present in theelectrical oil composition of the present invention in an amount in therange of from 0.05 to 5 wt. %, more preferably in an amount in the rangeof from 0.1 to 2 wt. % and most preferably in the range of from 0.1 to0.8 wt. %, based on the total weight of the electrical oil composition.

In a preferred embodiment of the present invention, the one or more baseoils (B) are base oils having a kinematic viscosity at 100° C. of notmore than 3.5 mm²/s, more preferably in the range of from 0.8 to 3mm²/s.

The one or more base oils (B) in the present invention preferably have asulphur content of less than 2 wt. %, more preferably less than 0.5 wt.% and most preferably less than 0.1 wt. %, as measured by ISO 14596,based on the total weight of the one or more base oils (B).

The one or more base oils (B) as hereinbefore described may beconveniently prepared by vacuum distillation, followed by solventextraction, hydrofining, hydrogenation and hydrocracking. Paraffinicoils may be de-waxed or hydroisomerised to improve the pour point.

Said one or more base oils (B) may also be conveniently prepared byFischer-Tropsch synthesis.

In a preferred embodiment of the present invention, said one or morebase oils (B) are selected from one or more mineral-derived paraffinicoils, one or more mineral-derived naphthenic oils, one or moreFischer-Tropsch derived base oils and mixtures thereof.

Particularly preferred paraffinic base oils (B) that may be used includeGroup I, Group II and Group III base oils.

By “Group I” base oils, “Group II” base oils and “Group III”, in thepresent invention are meant base oils according to the definitions ofAmerican Petroleum Institute (API) categories I and II. Such APIcategories are defined in API Publication 1509, 15th Edition, AppendixE, April 2002.

Group I base oils contain less than 90% saturates (according to ASTMD2007) and/or greater than 0.03% sulphur (according to ASTM D2622,D4294, D4927 or D3120) and have a viscosity index of greater than orequal to 80 and less than 120 (according to ASTM D2270).

Group II base oils contain greater than or equal to 90% saturates andless than or equal to 0.03% sulphur and have a viscosity index ofgreater than or equal to 80 and less than 120, according to theaforementioned ASTM methods.

Group III base oils contain greater than or equal to 90% saturates andless than or equal to 0.03% sulphur and have a viscosity index ofgreater than 120, according to the afore-mentioned ASTM methods.

Naphthenic base oils are defined as Group V base oils according to API.

The base oil composition may thus comprise a mineral-derived base oil ofthe so-called paraffinic type or naphthenic type. Such base oils areobtained by refinery processes starting from paraffinic and naphtheniccrude feeds.

Mineral-derived paraffin base oils are defined by a viscosity index ofgreater than 70, preferably greater than 90. Said base oils are producedfrom feedstocks rich in paraffins.

Mineral-derived naphthenic base oils for the purpose of the presentinvention are defined as having a pour point of below −20° C. and aviscosity index of below 70. Such base oils are produced from feedstocksrich in naphthenes and low in wax content and are used mainly forlubricants in which colour and colour stability are important, and VIand oxidation stability are of secondary importance.

Mineral-derived naphthenic and paraffin base oils are well known anddescribed in more detail in “Lubricant base oil and wax processing”,Avilino Sequeira, Jr., Marcel Dekker, Inc, New York, 1994, ISBN0-8247-9256-4, pages 28-35.

Fischer-Tropsch derived base oils may be conveniently used as the baseoil in the lubricating oil composition of the present invention, forexample, the Fischer-Tropsch derived base oils disclosed in EP-A-776959,EP-A-668342, WO-A-97/21788, WO-A-00/15736, WO-A-00/14188, WO-A-00/14187,WO-A-00/14183, WO-A-00/14179, WO-A-00/08115, WO-A-99/41332,EP-A-1029029, WO-A-01/18156 and WO-A-01/57166.

The one or more base oils (B) are preferably present in the electricaloil composition of the present invention in a total amount of at least80 wt. %, more preferably in a total amount in the range of from 90 to99.95 wt. %, based on the total weight of the electrical oilcomposition.

Further base oils and other synthetic base oil components may be presentin the electrical oil formulation, including base oils having akinematic viscosity at 100° C. which is greater than the kinematicviscosity at 100° C. of each of the one or more base oils (B). Such baseoils may include, but are not limited to, esters, poly alpha olefins, aspreferably obtained by oligomerisation of an olefinic compound and polyalkylene glycols.

The electrical oil composition of the present invention preferably has asulphur content of below 0.3 wt. % and even more preferably below 0.15wt. %, as measured by ISO 14596, with respect to the total weight of theelectrical oil composition.

The source of the majority of the sulphur in the electrical oilformulation will be the sulphur as contained in the base oil componentstherein.

In a preferred embodiment of the present invention, the electrical oilcomposition is a non-corrosive electrical oil, as measured according tothe CIGRE A2.32.01 Covered Conduct Deposition test (corrosive sulphur)and/or according to ASTM D 1275 B test. That is to say, in a preferredembodiment of the present invention, the electrical oil compositionpasses the CIGRE A2.32.01 Covered Conduct Deposition test for corrosivesulphur and/or the ASTM D 1275 B test for corrosive sulphur.

The electrical oil composition of the present invention preferably has akinematic viscosity at 100° C. of less than 5 mm²/sec, more preferablyless than 4 mm²/sec, most preferably less than 3 mm²/sec.

The flash point of the electrical oil composition as measured by ASTMD92 may be greater than 120° C., preferably greater than 135° C. Thehigher flash points are desirable for applications where peaktemperatures can exceed the average oil temperature, for instance inapplications under high temperature and/or with restricted heattransmission potential. Examples are electric transformers and electricengines.

In addition to base oils, the electrical oil composition of the presentinvention may comprise one or more additives.

For example, the electrical oil composition of the present invention maycomprise one or more metal passivators, in particular one or more copperpassivators.

Metal passivators or electrostatic discharge depressants, sometimes alsoreferred as metal deactivators, that may be conveniently used includeN-salicylideneethylamine, N,N′-disalicylideneethyldiamine,triethylenediamine, ethylenediamminetetraacetic acid, phosphoric acid,citric acid and gluconic acid. More preferred compounds are lecithin,thiadiazole, imidazole and pyrazole and derivatives thereof. Even morepreferred compounds are benzotriazoles and their derivatives.

Most preferred are the compounds according to formula (I) or even morepreferred the optionally substituted benzotriazole compound representedby the formula (II)

wherein R⁴ may be hydrogen or a group represented by the formula (III)

or by the formula (IV)

wherein:

-   c is 0, 1, 2 or 3;-   R¹ and R² are hydrogen or the same or different straight or branched    alkyl groups of 1-18 carbon atoms,-   preferably a branched alkyl group of 1-12 carbon atoms;-   R³ is a straight or branched C₁₋₄ alkyl group,-   preferably R³ is methyl or ethyl and C is 1 or 2; R⁵ is a methylene    or ethylene group; R⁶ and R⁷ are the same or different alkyl groups    of 3-15 carbon atoms, preferably of 4-9 carbon atoms.

Preferred compounds are 1-[bis(2-ethylhexyl)-aminomethyl)benzotriazole,methylbenzotriazole, dimethylbenzotriazole, ethylbenzotriazole,ethylmethylbenzotriazole, diethylbenzotriazole and mixtures thereof.Other preferred compounds include(N-Bis(2-ethylhexyl)-aminomethyl-tolutriazole, non-substitutedbenzotriazole, and 5-methyl-1H-benzotriazole. Examples of copperpassivator additives as described above are described in U.S. Pat. No.5,912,212, EP-A-1054052 and in US-A-2002/0109127. These benzotriazolecompounds are preferred because they also act as an electrostaticdischarge depressant, which is beneficial when an oil formulation isused as an electrical oil.

Metal passivator additives such as those described above arecommercially available under the trade designations “BTA”, “TTA”,“IRGAMET 39”, “IRGAMET 30” and “IRGAMET 38S” from CIBA Ltd BaselSwitzerland, also traded under the trade name “Reomet” by CIBA.

The content of the above metal passivator in the electrical oilcomposition of the present invention is preferably above 1 mg/kg andmore preferably above 5 mg/kg. A practical upper limit may varydepending on the specific application of the electrical oil composition.For example, when desiring improved dielectric discharge tendencies ofthe oil, it may be desired to add a high concentration of the metalpassivator additive. This concentration may be up to 3 wt. %, preferablyhowever in the range of from 0.001 to 1 wt. %. However, such compoundsmay be advantageously used at concentrations below 1000 mg/kg and morepreferably below 300 mg/kg.

The electrical oil composition of the present invention may comprise oneor more anti-oxidant additives.

Anti-oxidants that may be conveniently used are so-called hinderedphenolic or amine anti-oxidants, for example naphthols, stericallyhindered monohydric, dihydric and trihydric phenols, sterically hindereddinuclear, trinuclear and polynuclear phenols, alkylated or styrenateddiphenylamines or ionol derived hindered phenols.

Sterically hindered phenolic anti-oxidants of particular interest may beselected from the group consisting of 2,6-di-tert-butylphenol (availableunder the trade designation “IRGANOX™ L 140” from CIBA), ditert-butylated hydroxytoluene (“BHT”),methylene-4,4′-bis-(2.6-tert-butylphenol), 2,2′-methylenebis-(4,6-di-tert-butylphenol),1,6-hexamethylene-bis-(3,5-di-tert-butyl-hydroxyhydrocinnamate)(available under the trade designation “IRGANOX™ L109” from CIBA),((3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)methyl)thio)acetic acid,C₁₀-C₁₄isoalkyl esters (available under the trade designation “IRGANOX™L118” from CIBA), 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid,C₇-C₉alkyl esters (available under the trade designation “IRGANOX™ L135”from CIBA,)tetrakis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionyloxymethyl)methane(available under the trade designation “IRGANOX™ 1010” from CIBA),thiodiethylene bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate (availableunder the trade designation “IRGANOX™ 1035” from CIBA), octadecyl3,5-di-tert-butyl-4-hydroxyhydrocinnamate (available under the tradedesignation “IRGANOX™ 1076” from CIBA) and2,5-di-tert-butylhydroquinone.

Particularly preferred anti-oxidants are di-tert-butylatedhydroxytoluene (“BHT”) and 3,5-di-tert-butyl-4-hydroxy-hydrocinnamicacid-C₇-C₉-alkyl ester.

Examples of amine anti-oxidants that may be conveniently used includearomatic amine anti-oxidants for exampleN,N′-Di-isopropyl-p-phenylenediamine,N,N′-di-sec-butyl-p-phenylenediamine,N,N′-bis(1,4-dimethyl-pentyl)-p-phenylenediamine,N,N′-bis(1-ethyl-3-methyl-pentyl)-p-phenylene-diamine,N,N′-bis(l-methyl-heptyl)-p-phenylenediamine,N,N′-dicyclohexyl-p-phenylene-diamine, N,N′-diphenyl-p-phenylenediamine,N,N′-di(naphthyl-2-)-p-phenylenediamine,N-isopropyl-N′-phenyl-p-phenylenediamine,N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine,N-(1-methylheptyl)-N′-phenyl-p-phenylenediamine,N′-cyclohexyl-N′-phenyl-p-phenylenediamine,4-(p-toluene-sulfoamido)diphenylamine,N,N′-dimethyl-N,N′-di-sec-butyl-p-phenylenediamine, diphenylamine,N-allyldiphenylamine, 4-isopropoxy-diphenylamine,N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, octylateddiphenylamine, e.g. p,p′-di-tert-octyldiphenylamine,4-n-butylaminophenol, 4-butyrylaminophenol, 4-nonanoylaminophenol,4-dodecanoylaminophenol, 4-octadecanoylaminophenol,di(4-methoxyphenyl)amine,2,6-di-tert-butyl-4-dimethyl-aminomethylphenol,2,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane,N,N,N′,N′-tetramethyl-4,4′-diaminodiphenylmethane,1,2-di(phenylamino)ethane, 1,2-di[(2-methylphenyl)amino]ethane,1,3-di-(phenylamino)propane, (o-tolyl)biguanide,di[4-(1′,3′-dimethylbutyl)phenyl]amine, tert-octylatedN-phenyl-1-naphthylamine, mixture of mono- and dialkylatedtert-butyl-/tert-octyldiphenylamines,2,3-dihydro-3,3-dimethyl-4H-1,4-benzothiazine, phenothiazine, N-,tert-octylated phenothiazine, 3,7-di-tert-octylphenothiazine. Inaddition, amine anti-oxidants according to formula VIII and IX of EP-A-1054 052, which compounds are also described in U.S. Pat. No. 4,824,601may also be conveniently used.

The content of the one or more anti-oxidant additives is preferably lessthan 2 wt. % and more preferably less than 1 wt. %, even more preferablyless than 0.6 wt. % and most preferably less than 0.3 wt. %, withrespect to the total weight of the electrical oil composition.

Further additives that may also be present in the electrical oilcomposition of the present invention are dependent upon the specificapplication of the electrical oil composition.

Examples of possible further additives are detergents and pour pointdepressants. Specific examples of such additives are described in forexample Kirk-Othmer Encyclopedia of Chemical Technology, 3^(rd) edition,volume 14, pages 477-526.

The detergent may conveniently be an over-based metallic detergent, forexample the phosphonate, sulfonate, phenolate or salicylate types asdescribed in the above referred to General Textbook.

Preferred pour point depressants are hydrocarbon or oxygenatedhydrocarbon type pour point depressants.

As high additive treat rates can have adverse effects on otherproperties than oxidation stability in an electrical oil composition, inone embodiment of the present invention there is provided an electricaloil composition comprising (A) de-asphalted cylinder oil (DACO) having abenzo[a]pyrene content of not more than 1 mg/kg and a total content ofbenz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene,benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene and dibenz[a,h]anthracene of not more than 10 mg/kg; and (B) one or more base oilseach having a viscosity of not more than 4.0 mm²/s at 100° C., whereinsaid composition does not contain any anti-oxidant additives.

In a preferred embodiment of the present invention, there is provided anelectrical oil composition comprising (A) de-asphalted cylinder oil(DACO) having a benzo[a]pyrene content of not more than 1 mg/kg and atotal content of benz[a]anthracene, chrysene, benzo[b]fluoranthene,benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene,benzo[a]pyrene and dibenz[a, h]anthracene of not more than 10 mg/kg; and(B) one or more base oils each having a viscosity of not more than 4.0mm²/s at 100° C., wherein said composition does not contain anyadditives.

The electrical oil composition of the present invention may findparticular application in switch gears, transformers, regulators,circuit breakers, power plant reactors, shunt reactors, cables and otherelectrical equipment.

In order to improve the gassing tendency of the electrical oilcomposition of the present invention, it is preferred to add between0.05 and 10 wt %, preferably between 0.1 and 5 wt % of an aromaticcompound. Preferred aromatic compounds are for exampletertrahydronaphthalene, diethylbenzene, di-isopropylbenzene, a mixtureof alkylbenzenes as commercially obtainable as “Shell Oil 4697” or“Shellsol A 150” both “Shell” products obtainable from Shell DeutschlandGmbH.

A preferred electrical oil composition of the present inventioncomprises a mixture of 2,6-di-t-butyl phenol and 2,6-di-t-butyl cresol.Preferably the oil formulation comprises between 0.1 and 3 wt % of2,6-di-t-butyl phenol and 0.1 to 2 wt % of 2,6-di-t-butyl cresol in aweight ratio of between 1:1 and 1:1.5.

The electrical oil composition according to the present invention ispreferably subjected to a clay treatment.

Clay treatment is a well known treatment to remove polar compounds fromelectrical oil compositions. It is performed in order to further improvethe colour, chemical and thermal stability of such compositions. It maybe performed prior to adding the additives hereinbefore described on apartly formulated electrical oil composition.

Clay treatment processes are for example described in Lubricant base oiland wax processing, Avilino Sequeira, Jr., Marcel Dekker, Inc, New York,1994, ISBN 0-8247-9256-4, pages 229-232.

Preferably, additive components such as copper passivators andanti-oxidants are added after the clay treatment.

The electrical oil composition of the present invention may find use inapplications which have to start up regularly, especially more than 10times per year at a temperature of below 0° C., more preferably below−5° C., wherein the temperature of the oil when the application isrunning is above 0° C. Examples of such applications are as lowtemperature switch gear oils, transformers, regulators, circuitbreakers, power plant reactors, switch gear, cables, electricalequipment. Such applications are well known to the skilled person anddescribed for example in Lubricants and related products, DieterKlamann, Verlag Chemie GmbH, Weinhem, 1984, pages 330-339.

The electrical oil composition as herein before described may beconveniently prepared by admixing (A) de-asphalted cylinder oil (DACO)having a benzo[a]pyrene content of not more than 1 mg/kg and a totalcontent of benz[a]anthracene, chrysene, benzo[b]fluoranthene,benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene,benzo[a]pyrene and dibenz[a, h]anthracene of not more than 10 mg/kg with(B) one or more base oils each having a viscosity of not more than 4.0mm²/s at 100° C., and, optionally, one or more additives as hereinbefore described.

In the present invention, electrical oil compositions comprising (A)de-asphalted cylinder oil (DACO) having a benzo[a]pyrene content of notmore than 1 mg/kg and a total content of benz[a]anthracene, chrysene,benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene,benzo[e]pyrene, benzo[a]pyrene and dibenz[a, h]anthracene of not morethan 10 mg/kg; and (B) one or more base oils each having a viscosity ofnot more than 4.0 mm²/s at 100° C. have been surprisingly found to havegood oxidation stability, but also to avoid the need for R45 labelling.

In another embodiment of the present invention, there is provided amethod of avoiding R 45 toxicological labelling for an electrical oil byutilising an electrical oil as hereinbefore described.

The present invention further provides the use of the composition ashereinbefore described as an electrical oil for application in one ormore of transformers, regulators, circuit breakers, power plantreactors, shunt reactors, switch gears, cables and electrical equipment.

The invention will be described with reference to the following Exampleswhich are not intended to limit the scope of the invention in any way.

EXAMPLES

Table 1 indicates the formulations that were tested and the experimentalresults thereon. Table 2 indicates the properties of the base oils inTable 1.

TABLE 1 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex.5 Naphthenic Base Oil-1 wt. % 100 98.5 97 98.5 99 96.5 98 — NaphthenicBase Oil-2 wt. % — — 3 — — 3 1.5 — Gas to Liquids Base Oil wt. % — — — —— — — 99 DACO* wt. % — — — 1.5 1 0.5 0.5 1.0 DAE** (SN 150 extract) wt.% — 1.5 — — — — — — Clay treatment “Tonsil 411”*** wt. % 0.4 0.4 — 0.4 —0.4 1.0 — “Irgamet 39” metal passivator mg/kg — — — — — — 100 —Kinematic viscosity (100° C.) of mm²/s 2.1 2.1 2.1 2.2 2.1 2.1 2.1 2.4composition (ISO 3104) Sulphur content of composition wt. % 0.001 0.060.04 0.06 0.04 0.05 0.04 <0.001 (ISO 14596) BAADER AGEING TEST 140h/110° C. (DIN 51554) Neutralisation Number after test mg KOH/g 0.620.06 0.12 0.12 0.11 0.08 0.07 0.05 Saponification Number after test mgKOH/g 2.46 0.22 0.56 0.44 0.5 0.41 0.3 0.07 IEC 61125 C Oxidation test164 H/120° C. Total Acidity mg KOH/g 3.5 0.64 0.76 Nm2 Nm2 0.39 0.29 Nm2Labelling required according to EU no R 45 no no no No no no SubstanceDirective 67/548/EEC CIGRE A2.32.01 Covered Conduct Nm1 Nm2 pass Nm2 Nm2Pass pass pass Deposition test ASTM D 1275 B Copper Corrosion Test Nm1Nm2 pass Nm2 Nm2 Pass pass pass *DACO = de-asphalted cylinder oil. **DAE= distillate aromatic extract. ***= not a component. Indicates amount of“Tonsil 411” used in clay treatment. Nm1 = not measured as sludgeproduced was very high. Nm2 = not measured.

TABLE 2 Naphthenic Naphthenic GTL base Base Oil-1 Base Oil-2 oil DAEDACO Colour (ASTM) ISO L0.5 L0.5 L0.5 D8.0 D8.0 2049 Density at 15° C.kg/m³ ISO 878 909 803 985 980 12185 Flashpoint (COC) ° C. ISO 154 162166 180 300 2592 Pour Point ° C. ISO −60 −60 −48 −20 +15 3016 KinematicViscosity @ 100° C. mm²/s ISO 2.1 2.4 2.4 4.5 60 3104 Sulphur (X-Ray)wt. % ISO 0.001 1.1 <0.001 4 4 14596 Benzo[a]pyrene content mg/kg 12 0.2Sum of 8 PAH content* mg/kg 183 2.1 *Total content of benz[a]anthracene,chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene,benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene anddibenz[a,h]anthracene

Oxidation stability was assessed by the so-called Baader ageing testaccording to DIN 51554 and the IEC 61125 C Oxidation test 164H/120° C.

Comparative Example 1 represents a naphthenic base oil. Both theneutralisation number and saponification number after the Baader testare extremely high and indicate a severe oxidative degradation of saidoil resulting in acids and ester structures. The total acidity in theIEC 61125C test is also unacceptably high.

Comparative Example 2 represents a typical electrical oil formulationcomprising naphthenic base oil and distillate aromatic extract. Whilstsaid formulation has excellent ageing properties, in accordance with EUSubstance Directive 67/548/EEC, it requires labelling with R 45 and “T”(skull and cross bones) due to the use of DAE (which is carcinogenic) asblend component.

Comparative Example 3 is a blend of a high sulphur and a low sulphurcontaining naphthenic base oil. Said formulation has a higherneutralisation number and a higher saponification number thanComparative Example 2 which represents the industry reference for a highquality un-inhibited electrical oil.

Example 1 represents an electrical oil composition according to thepresent invention, which composition comprise a blend of naphthenic baseoil with DACO to match the sulphur content of Comparative Example 2. Notonly are the neutralisation number and the saponification numbers forExample 1 good, but in addition, said composition also avoids the needfor labelling according to EU Substance Directive 67/548/EEC.

Example 2 represents another electrical oil composition according to thepresent invention, which composition comprise a blend of naphthenic baseoil with DACO. In addition to having good values for the neutralisationnumber and the saponification numbers after the Baader ageing test, saidcomposition also avoids the need for labelling according to EU SubstanceDirective 67/548/EEC.

Example 3 represents an electrical oil composition according to thepresent invention, which composition comprises a blend of two naphthenicoils with DACO. This formulation shows an improved neutralisation valueand saponification value when compared to Comparative Example 3.Furthermore, said composition also avoids the need for labellingaccording to EU Substance Directive 67/548/EEC.

Example 4 represents an electrical oil composition according to thepresent invention, which composition comprises a blend of two naphthenicoils with DACO and also contains a metal passivator. When compared withComparative Example 2, it is apparent that this formulation has a lowertotal acidity in the IEC 61125 C oxidation test.

Not only are the neutralisation and saponification numbers after theBaader ageing test and the acidity value in the IEC 61125 C test forExample 4 greatly improved as compared to Comparative Example 1, butsaid composition also avoids the need for labelling according to EUSubstance Directive 67/548/EEC.

Example 5 represents an electrical oil composition according to thepresent invention, which composition comprises a blend of aFisher-Tropsch derived base oil with DACO.

Thus, unlike the Comparative Examples, the electrical oil compositionsof Examples 1-5 not only avoid the need for labelling according to EUSubstance Directive 67/548/EEC, but also have good oxidation stability.

1. An electrical oil composition comprising (A) de-asphalted cylinderoil (DACO) having a benzo[a]pyrene content of not more than 1 mg/kg anda total content of benz[a]anthracene, chrysene, benzo[b]fluoranthene,benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene,benzo[a]pyrene and dibenz[a,h]anthracene of not more than 10 mg/kg; and(B) one or more base oils each having a viscosity of not more than 4.0mm2/s at 100° C.
 2. Electrical oil composition according to claim 1,wherein the one or more base oils (B) are selected from one or moremineral-derived paraffinic oils, one or more mineral-derived naphthenicoils, one or more Fischer-Tropsch derived base oils and mixturesthereof.
 3. Electrical oil composition according to claim 1, whereinsaid composition has been subjected to a clay treatment.
 4. Electricaloil composition according to claim 1, wherein said composition comprisesone or more pour point depressant additives.
 5. Electrical oilcomposition according to claim 1, wherein said composition comprises oneor more metal passivator additives.
 6. Electrical oil compositionaccording to claim 5, wherein said one or more metal passivatoradditives are benzotriazole derivatives.
 7. Electrical oil compositionaccording to claim 1, wherein said composition comprises one or moreanti-oxidants.
 8. Electrical oil composition according to claim 7,wherein said composition comprises di tert-butylated hydroxytoluene(BHT) as an anti-oxidant.
 9. Electrical oil composition according toclaim 1, wherein said composition passes the CIGRE A2.32.01 CoveredConduct Deposition test for corrosive sulphur and/or the ASTM D 1275 Btest for corrosive sulphur.
 10. Use of the composition according toclaim 1 as an electrical oil for application in one or more oftransformers, regulators, circuit breakers, power plant reactors, shuntreactors, switch gears, cables and electrical equipment.